Torque And Current Control Methods For Switching Variable Electric Drive Vehicles

ABSTRACT

A current command module is configured to, based on a direct current (DC) bus voltage for an electric motor of the vehicle, generate a d-axis current command for the electric motor and a q-axis current command for the electric motor. A voltage command module configured to generate voltage commands based on the d-axis current command and the q-axis current command. A battery switching control module is configured to: determine a voltage operating state of a battery based on the voltage commands; compare a battery parameter to at least one of a predetermined voltage parameter and a predetermined current parameter during a dwell time when a plurality of switches of the battery are open; and generate a switch control signal to transition at least one switch of the plurality of switches to cause the battery to operate in the voltage operating state based on the comparison.

The information provided in this section is for the purpose of generallypresenting the context of the disclosure. Work of the presently namedinventors, to the extent it is described in this section, as well asaspects of the description that may not otherwise qualify as prior artat the time of filing, are neither expressly nor impliedly admitted asprior art against the present disclosure.

The present disclosure relates to vehicle propulsion systems and moreparticularly to systems and methods for controlling an electric motor ofa vehicle.

Some types of vehicles include only an internal combustion engine thatgenerates propulsion torque. Hybrid vehicles include both an internalcombustion engine and one or more electric motors. Some types of hybridvehicles utilize the electric motor and the internal combustion enginein an effort to achieve greater fuel efficiency than if only theinternal combustion engine was used. Some types of hybrid vehiclesutilize the electric motor and the internal combustion engine to achievegreater torque output than the internal combustion could achieve byitself.

Some example types of hybrid vehicles include parallel hybrid vehicles,series hybrid vehicles, and other types of hybrid vehicles. In aparallel hybrid vehicle, the electric motor works in parallel with theengine to combine power and range advantages of the engine withefficiency and regenerative braking advantages of electric motors. In aseries hybrid vehicle, the engine drives a generator to produceelectricity for the electric motor, and the electric motor drives atransmission. This allows the electric motor to assume some of the powerresponsibilities of the engine, which may permit the use of a smallerand possibly more efficient engine. In pure electric vehicles, withoutan internal combustion engine, batteries serve as the only energy sourceand only electric motors are used for vehicle propulsion.

SUMMARY

In a feature, an electric motor control system includes: a currentcommand module configured to, based on a motor torque request, a motorspeed, a direct current (DC) bus voltage for an electric motor of thevehicle, generate a d-axis current command for the electric motor and aq-axis current command for the electric motor; a voltage command moduleconfigured to generate voltage commands based on the d-axis currentcommand and the q-axis current command; and a battery switching controlmodule configured to: determine a voltage operating state of a batterybased on the voltage commands; compare a battery parameter to at leastone of a predetermined voltage parameter and a predetermined currentparameter during a dwell time when a plurality of switches of thebattery are open; and generate a switch control signal to transition atleast one switch of the plurality of switches to cause the battery tooperate in the voltage operating state based on the comparison.

In further features, wherein the dwell time corresponds to a time periodbetween a first voltage operating state and a second voltage operatingstate.

In further features, wherein the battery parameter comprises at leastone of a measured voltage and a measured current.

In further features, an inverter module is connected between the batteryand the electric motor.

In further features, the inverter module is configured to convertvoltage provided by the battery and provide the converted voltage to themotor.

In further features, a capacitor is disposed between the battery and theinverter module, wherein the capacitor stores energy provided by thebattery.

In further features, a capacitance value of the capacitor is selectedaccording to

C=2*(Tdw−Δ(t))*(rpm*Nm*2 pi/60)/([Vst2]²−[Vst1]²),

where Tdw corresponds to the dwell time, Vst2 is a voltage correspondingto a second voltage operating state, Vst1 is a voltage corresponding toa first voltage operating state, rpm corresponds to revolutions perminute of the motor, Nm corresponds to a torque of the motor, and Δ(t)is a predetermined slack time parameter.

In further features, the battery comprises at least a first battery anda second battery.

In further features, the first battery includes a rating of greater than60 volts direct current (DC), and the second battery includes a ratingof greater than 60 volts DC.

In further features, the plurality of switches are arranged so that thefirst battery and the second battery operate in parallel in a firstvoltage operating state and operate in series in a second voltageoperating state.

In a feature, an electric motor control method includes: based on amotor torque request, a motor speed, a direct current (DC) bus voltagefor an electric motor of the vehicle, generating a d-axis currentcommand for the electric motor and a q-axis current command for theelectric motor; generating voltage commands based on the d-axis currentcommand and the q-axis current command; determining a voltage operatingstate of a battery based on the voltage commands; comparing a batteryparameter to at least one of a predetermined voltage parameter and apredetermined current parameter during a dwell time when a plurality ofswitches of the battery are open; and generating a switch control signalto transition at least one switch of the plurality of switches to causethe battery to operate in the voltage operating state based on thecomparison.

In further features, the dwell time corresponds to a time period betweena first voltage operating state and a second voltage operating state.

In further features, the battery parameter comprises at least one of ameasured voltage and a measured current.

In further features, the method further includes selectively switchingan inverter module connected between the battery and the electric motor.

In further features, the method further includes by the inverter module,converting voltage provided by the battery and providing the convertedvoltage to the motor.

In further features, the method further includes, by a capacitorconnected between the battery and the inverter module, storing energyprovided by the battery.

In further features, the method further includes selecting a capacitanceof the capacitor according to

C=2*(Tdw−Δ(t))*(rpm*Nm*2 pi/60)/([Vst2]²−[Vst1]²),

where Tdw corresponds to the dwell time, Vst2 is a voltage correspondingto a second voltage operating state, Vst1 is a voltage corresponding toa first voltage operating state, rpm corresponds to revolutions perminute of the motor, Nm corresponds to a torque of the motor, and Δ(t)is a predetermined slack time parameter.

In further features, the battery comprises at least a first battery anda second battery.

In further features, the first battery includes a rating of greater than60 volts direct current (DC), and the second battery includes a ratingof greater than 60 volts DC.

In further features, the method further includes: switching theplurality of switches such that the first battery and the second batteryare connected in parallel in a first voltage operating state; andswitching the plurality of switches such that the first battery and thesecond battery are connected in series in a second voltage operatingstate.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description, the claims and the drawings. Thedetailed description and specific examples are intended for purposes ofillustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of an example vehicle system;

FIG. 2 is a functional block diagram of an example propulsion controlsystem;

FIG. 3 is a schematic including an example implementation of an invertermodule and a battery;

FIG. 4 is a functional block diagram including an example implementationof a motor control module;

FIG. 5 is a functional block diagram of an example implementation of abattery switching control module;

FIG. 6 is a graph illustrating capacitor voltage as a function of timebased on an voltage operating state of the battery; and

FIGS. 7 and 8 are flowcharts depicting example methods of controllingthe battery.

In the drawings, reference numbers may be reused to identify similarand/or identical elements.

DETAILED DESCRIPTION

An internal combustion engine of a vehicle combusts air and fuel withincylinders to generate propulsion torque. The engine outputs torque towheels of the vehicle via a transmission. Some types of vehicles may notinclude an internal combustion engine, such as a pure electric vehicle,or the internal combustion engine may not be mechanically coupled to adriveline of the vehicle.

An electric motor may be mechanically coupled to a shaft of thetransmission. Under some circumstances, a control module of the vehiclemay apply power to the electric motor from a battery to cause theelectric motor to output torque for vehicle propulsion. Under othercircumstances, the control module may disable power flow to the electricmotor and allow the transmission to drive rotation of the electricmotor. The electric motor generates power when driven by thetransmission. Power generated by the electric motor can be used torecharge the battery when a voltage generated via the electric motor isgreater than a voltage of the battery. An inverter can be used to boostthe motor voltage above the battery voltage when the motor voltage isless than the battery voltage.

The control module determines a d-axis (direct-axis) current command anda q-axis (quadrature-axis) current command for the electric motor basedon a requested torque and speed output of the electric motor. A voltagecommand module generates voltage commands for the electric motor basedon the d-axis current command and the q-axis current command. Accordingto the present disclosure, a battery switching control module candetermine a voltage operating state of a battery based on the voltagecommands and compare a battery system parameter to a predeterminedvoltage parameter or a predetermined current parameter during a dwelltime when a plurality of switches of the battery are open. Based on thecomparison, the battery switching control module generates a switchcontrol signal to transition at least one switch to cause the battery tooperate in the voltage operating state.

Referring now to FIG. 1, a functional block diagram of an examplevehicle system is presented. While a vehicle system for a hybrid vehicleis shown and will be described, the present disclosure is alsoapplicable to electric vehicles that do not include an internalcombustion engine, fuel cell vehicles, autonomous vehicles, and othertypes of vehicles. Also, while the example of a vehicle is provided, thepresent application is also applicable to non-vehicle implementations.

An engine 102 may combust an air/fuel mixture to generate drive torque.An engine control module (ECM) 114 controls the engine 102. For example,the ECM 114 may control actuation of engine actuators, such as athrottle valve, one or more spark plugs, one or more fuel injectors,valve actuators, camshaft phasers, an exhaust gas recirculation (EGR)valve, one or more boost devices, and other suitable engine actuators.In some types of vehicles (e.g., electric vehicles), the engine 102 maybe omitted.

The engine 102 may output torque to a transmission 195. A transmissioncontrol module (TCM) 194 controls operation of the transmission 195. Forexample, the TCM 194 may control gear selection within the transmission195 and one or more torque transfer devices (e.g., a torque converter,one or more clutches, etc.).

The vehicle system includes one or more electric motors, such aselectric motor 198. An electric motor can act as either a generator oras a motor at a given time. When acting as a generator, an electricmotor converts mechanical energy into electrical energy. The electricalenergy can be, for example, used to charge a battery 199. When acting asa motor, an electric motor generates torque that may be used, forexample, for vehicle propulsion. While the example of one electric motoris provided, the vehicle may include more than one electric motor.

A motor control module 196 controls power flow from the battery 199 tothe electric motor 198 and from the electric motor 198 to the battery199. The motor control module 196 applies electrical power from thebattery 199 to the electric motor 198 to cause the electric motor 198 tooutput positive torque, such as for vehicle propulsion. The battery 199may include, for example, one or more battery packs.

The electric motor 198 may output torque, for example, to an input shaftof the transmission 195 or to an output shaft of the transmission 195. Aclutch 200 may be engaged to couple the electric motor 198 to thetransmission 195 and disengaged to decouple the electric motor 198 fromthe transmission 195. One or more gearing devices may be implementedbetween an output of the clutch 200 and an input of the transmission 195to provide a predetermined ratio between rotation of the electric motor198 and rotation of the input of the transmission 195.

The motor control module 196 may also selectively convert mechanicalenergy of the vehicle into electrical energy. More specifically, theelectric motor 198 generates and outputs power via back EMF when theelectric motor 198 is being driven by the transmission 195 and the motorcontrol module 196 is not applying power to the electric motor 198 fromthe battery 199. The motor control module 196 may charge the battery 199via the power output by the electric motor 198. This may be referred toas regeneration.

Referring now to FIG. 2, a functional block diagram of an examplepropulsion control system is presented. A driver torque module 204determines a driver torque request 208 based on driver input 212. Thedriver input 212 may include, for example, an accelerator pedal position(APP), a brake pedal position (BPP), and/or cruise control input. Invarious implementations, the cruise control input may be provided by anadaptive cruise control system that attempts to maintain at least apredetermined distance between the vehicle and objects in a path of thevehicle. The driver torque module 204 determines the driver torquerequest 208 based on one or more lookup tables that relate the driverinputs to driver torque requests. The APP and BPP may be measured usingone or more APP sensors and BPP sensors, respectively.

The driver torque request 208 may be an axle torque request. Axletorques (including axle torque requests) refer to torque at the wheels.As discussed further below, propulsion torques (including propulsiontorque requests) are different than axle torques in that propulsiontorques may refer to torque at a transmission input shaft.

An axle torque arbitration module 216 arbitrates between the drivertorque request 208 and other axle torque requests 220. Axle torque(torque at the wheels) may be produced by various sources including theengine 102 and/or one or more electric motors, such as the electricmotor 198. Examples of the other axle torque requests 220 include, butare not limited to, a torque reduction requested by a traction controlsystem when positive wheel slip is detected, a torque increase requestto counteract negative wheel slip, brake management requests to reduceaxle torque to ensure that the axle torque does not exceed the abilityof the brakes to hold the vehicle when the vehicle is stopped, andvehicle over-speed torque requests to reduce the axle torque to preventthe vehicle from exceeding a predetermined speed. The axle torquearbitration module 216 outputs one or more axle torque requests 224based on the results of arbitrating between the received axle torquerequests 208 and 220.

In hybrid vehicles, a hybrid module 228 may determine how much of theone or more axle torque requests 224 should be produced by the engine102 and how much of the one or more axle torque requests 224 should beproduced by the electric motor 198. The example of the electric motor198 will be continued for simplicity, but multiple electric motors maybe used. The hybrid module 228 outputs one or more engine torquerequests 232 to a propulsion torque arbitration module 236. The enginetorque requests 232 indicate a requested torque output of the engine102.

The hybrid module 228 also outputs a motor torque request 234 to themotor control module 196. The motor torque request 234 indicates arequested torque output (positive or negative) of the electric motor198. In vehicles where the engine 102 is omitted (e.g., electricvehicles) or is not connected to output propulsion torque for thevehicle, the axle torque arbitration module 216 may output one axletorque request and the motor torque request 234 may be equal to thataxle torque request. In the example of an electric vehicle, the ECM 114may be omitted, and the driver torque module 204 and the axle torquearbitration module 216 may be implemented within the motor controlmodule 196.

The propulsion torque arbitration module 236 converts the engine torquerequests 232 from an axle torque domain (torque at the wheels) into apropulsion torque domain (e.g., torque at an input shaft of thetransmission). The propulsion torque arbitration module 236 arbitratesthe converted torque requests with other propulsion torque requests 240.Examples of the other propulsion torque requests 240 include, but arenot limited to, torque reductions requested for engine over-speedprotection and torque increases requested for stall prevention. Thepropulsion torque arbitration module 236 may output one or morepropulsion torque requests 244 as a result of the arbitration.

An actuator control module 248 controls actuators 252 of the engine 102based on the propulsion torque requests 244. For example, based on thepropulsion torque requests 244, the actuator control module 248 maycontrol opening of a throttle valve, timing of spark provided by sparkplugs, timing and amount of fuel injected by fuel injectors, cylinderactuation/deactivation, intake and exhaust valve phasing, output of oneor more boost devices (e.g., turbochargers, superchargers, etc.),opening of an EGR valve, and/or one or more other engine actuators. Invarious implementations, the propulsion torque requests 244 may beadjusted or modified before use by the actuator control module 248, suchas to create a torque reserve.

The motor control module 196 controls switching of an inverter module256 based on the motor torque request 234. Switching of the invertermodule 256 controls power flow from the battery 199 to the electricmotor 198. As such, switching of the inverter module 256 controls torqueof the electric motor 198. The inverter module 256 also converts powergenerated by the electric motor 198 and outputs power to the battery199, for example, to charge the battery 199.

The inverter module 256 includes a plurality of switches. The switchesare switched to convert DC power from the battery 199 into alternatingcurrent (AC) power and apply the AC power to the electric motor 198 todrive the electric motor 198. For example, the inverter module 256 mayconvert the DC power from the battery 199 into n-phase AC power andapply the n-phase AC power to (e.g., a, b, and c, or u, v, and w) nstator windings of the electric motor 198. In various implementations, nis equal to 3. Magnetic flux produced via current flow through thestator windings drives a rotor of the electric motor 198. The rotor isconnected to and drives rotation of an output shaft of the electricmotor 198.

In various implementations, one or more filters may be electricallyconnected between the inverter module 256 and the battery 199. The oneor more filters may be implemented, for example, to filter power flow toand from the battery 199. As an example, a filter including one or morecapacitors and resistors may be electrically connected in parallel withthe inverter module 256 and the battery 199.

FIG. 3 includes a schematic including an example implementation of theinverter module 256 and the battery 199. High (positive) and low(negative) sides 304 and 308 are connected to positive and negativeterminals, respectively, of the battery 199. The inverter module 256 isalso connected between the high and low sides 304 and 308.

The inverter module 256 includes three legs, one leg connected to eachphase of the electric motor 198. A first leg 312 includes first andsecond switches 316 and 320. The switches 316 and 320 each include afirst terminal, a second terminal, and a control terminal. Each of theswitches 316 and 320 may be an insulated gate bipolar transistor (IGBT),a field effect transistor (FET), such as a metal oxide semiconductor FET(MOSFET), or another suitable type of switch. In the example of IGBTsand FETs, the control terminal is referred to as a gate.

The first terminal of the first switch 316 is connected to the high side304. The second terminal of the first switch 316 is connected to thefirst terminal of the second switch 320. The second terminal of thesecond switch 320 may be connected to the low side 308. A node connectedto the second terminal of the first switch 316 and the first terminal ofthe second switch 320 is connected to a first phase (e.g., a) of theelectric motor 198.

The first leg 312 also includes first and second diodes 324 and 328connected anti-parallel to the switches 316 and 320, respectively. Inother words, an anode of the first diode 324 is connected to the secondterminal of the first switch 316, and a cathode of the first diode 324is connected to the first terminal of the first switch 316. An anode ofthe second diode 328 is connected to the second terminal of the secondswitch 320, and a cathode of the second diode 328 is connected to thefirst terminal of the second switch 320. When the switches 316 and 320are off (and open), power generated by the electric motor 198 istransferred through the diodes 324 and 328 when the output voltage ofthe electric motor 198 is greater than the voltage of the battery 199.This charges the battery 199. The diodes 324 and 328 form one phase of athree-phase rectifier.

The inverter module 256 also includes second and third legs 332 and 336.The second and third legs 332 and 336 may be (circuitry wise) similar oridentical to the first leg 312. In other words, the second and thirdlegs 332 and 336 may each include respective switches and diodes likethe switches 316 and 320 and the diodes 324 and 328, connected in thesame manner as the first leg 312. For example, the second leg 332includes switches 340 and 344 and anti-parallel diodes 348 and 352. Anode connected to the second terminal of the switch 340 and the firstterminal of the switch 344 is connected to a second stator winding(e.g., b) of the electric motor 198. The third leg 336 includes switches356 and 360 and anti-parallel diodes 364 and 368. A node connected tothe second terminal of the switch 356 and the first terminal of theswitch 360 is connected to a third stator winding (e.g., c) of theelectric motor 198.

As shown in FIG. 3, the battery 199 includes a first battery 370 and asecond battery 372. In an example implementation, the batteries 370, 372are direct current (DC) batteries. The battery 199 also includes a firstswitch 374, a second switch 376, and a third switch 378. The switches374, 376, and 378 each include a first terminal, a second terminal, anda control terminal. Each of the switches 374, 376, and 378 may be aninsulated gate bipolar transistor (IGBT), a field effect transistor(FET), such as a metal oxide semiconductor FET (MOSFET), or anothersuitable type of switch. In the example of IGBTs and FETs, the controlterminal is referred to as a gate.

As described herein, the motor control module 196 can also control theswitches 374, 376, and 378 allowing the motor 198 to operate at variablevoltages. For example, the batteries 370 and 372 may be four hundredvolt (400 V) DC batteries or other suitable high voltage (e.g., greaterthan 60 V) batteries. Thus, based on the configuration of the switches374, 376, and 378, the voltage provided to the motor may range betweenabout three hundred and fifty volts (350 V) and about seven hundredvolts (700 V). For example, when switches 374 and 378 are closed andswitch 376 is open, the battery 199 is operating in a first voltageoperating state and may provide about three hundred and fifty volts tothe inverter 256.

When switch 376 is closed and switches 374 and 378 are open, the battery199 is operating in a second voltage operating state and may provideabout seven hundred volts to the inverter 256. A capacitor 380 isconnected between terminals 304 and 308 to store charge. As shown inFIG. 3, the switches 374, 376, 378 are arranged so that the batteries370 and 372 operate in parallel in the first voltage operating state andoperate in series in a second voltage operating state.

FIG. 4 is a functional block diagram including an example implementationof the motor control module 196. An inverter switching control module404 controls switching of the switches 316 and 320 using pulse widthmodulation (PWM) signals. For example, the inverter switching controlmodule 404 may apply PWM signals to the control terminals of theswitches 316, 320, 340, 344, 356, and 360. When on, power flows from thebattery 199 to the electric motor 198 to drive the electric motor 198.

For example, the inverter switching control module 404 may applygenerally complementary PWM signals to the control terminals of theswitches 316 and 320 when applying power from the battery 199 to theelectric motor 198. In other words, the PWM signal applied to thecontrol terminal of the first switch 316 is opposite in polarity to thePWM signal applied to the control terminal of the second switch 320.Short circuit current may flow, however, when the turning on of one ofthe switches 316 and 320 overlaps with the turning off of the other ofthe switches 316 and 320. As such, the inverter switching control module404 may generate the PWM signals to turn both of the switches 316 and320 off during a deadtime period (T dead) before turning either one ofthe switches 316 and 320 on. With this in mind, generally complementarymay mean that two signals have opposite polarities for a majority oftheir periods when power is being output to the electric motor 198.Around transitions, however, both PWM signals may have the same polarity(off) for some overlap deadtime period.

The PWM signals provided to the switches of the second and third legs332 and 336 may also be generally complementary per leg. The PWM signalsprovided to the second and third legs 332 and 336 may be phase shiftedfrom each other and from the PWM signals provided to the switches 316and 320 of the first leg 312. For example, the PWM signals for each legmay be phase shifted from each other leg by 120° (360°/3 legs=120° shiftper leg). In this way, the currents through the stator windings (phases)of the electric motor 198 are phase shifted by 120° from each other.

A current command module 408 determines a d-axis current command (IdCommand) and a q-axis current command (Iq Command) for the electricmotor 198 based on the motor torque request 234, a (mechanical) rotorspeed 432 of the electric motor 198, and a DC bus voltage 410. Thecurrent command module 408 may determine the d and q-axis currentcommands, for example, using one or more equations and/or lookup tablesthat relate DC bus voltages, speeds, and motor torque requests to d andq-axis current commands. As discussed above, the DC bus voltage can varybased on the voltage operating state (e.g., about three hundred andfifty volts in the first voltage operating state and about 700 volts inthe second voltage operating state). When all of the battery switchesare open, the DC bus voltage may drop to or below a minimum DC busvoltage, such as approximately 100 volts.

A voltage sensor 411 measures the DC bus voltage 410 between the battery199 and the inverter module 256 (e.g., between the high and low sides304 and 308) and the voltage at the capacitor 380. The d-axis currentcommand and the q-axis current command are collectively illustrated by412. The axis of the field winding in the direction of the DC field iscalled the rotor direct axis or the d-axis. The axis that is 90 degreesafter the d-axis is called the quadrature axis or q-axis.

The rotor speed 432 is a (mechanical) rotational speed of the rotor ofthe electric motor 198. The rotor speed 432 may be measured, forexample, using a rotor speed sensor 436. In various implementations, therotor speed 432 may be determined by a rotor speed module based on oneor more other parameters, such change in position of the rotor over timewhere position is determined based on phase currents 440 (e.g., Ia, Ib,Ic) of the electric motor 198. Current sensors 442 may measure the phasecurrents 440, such as in the respective legs of the inverter module 256.In various implementations, one or more of the phase currents 440 may beestimated.

A rate limiting module 452 rate limits changes in the d-axis currentcommand and the q-axis current command. In other words, the ratelimiting module 452 may adjust the d-axis current command toward apresent value of the d-axis current command by up to a predeterminedamount during each control loop. The rate limiting module 452 may adjustthe q-axis current command toward a present value of the q-axis currentcommand by up to a predetermined amount during each control loop. Therate limiting module 452 outputs rate limited d-axis and q-axis currentcommands that result from the rate limiting. The rate limited d-axis andq-axis current commands are collectively illustrated by 454.

A voltage command module 456 determines voltage commands for voltages toapply to the respective phases of the electric motor 198 based on therate limited d-axis current command and the rate limited q-axis currentcommand, a d-axis current of the electric motor 198, and a q-axiscurrent of the electric motor 198. The d-axis current and the q-axiscurrent are collectively illustrated by 460. The voltage command module456 may determine the voltage commands 460 using one or more equationsand/or lookup tables that relate d and q axis current commands and d andq-axis currents to voltage commands. In various implementations, thevoltage command module 456 may generate the voltage commands 460 usingclosed-loop control to adjust the d and q-axis currents 444 toward or tothe rate limited d and q-axis current commands 454, respectively. Aframe of reference (FOR) module 448 may transform the phase currents 440into the d and q-axis currents 444 by applying a Clarke transform and aPark transform.

The inverter switching control module 404 determines final duty cyclesof the PWM signals to apply to the phases of the electric motor 198based on the respective voltage commands of the phases. For example, theinverter switching control module 404 may determine initial duty cyclecommands using one or more equations or lookup tables that relatevoltage commands to PWM duty cycles. The inverter switching controlmodule 404 determines the final duty cycle commands of the PWM signalsto apply to the phases based on the initial duty cycle commands of thephases, respectively, and the respective phase currents.

A battery switching control module 480 determines the switch controlsignals 481 to apply to the switches 374, 376, and 378 of the battery199 based on the voltage and/or current commands. For example, thebattery switching control module 480 may determine the switch controlusing one or more equations and/or lookup tables that relate the voltageand/or current commands to battery voltage levels (e.g., three hundredand fifty volts, seven hundred volts).

FIG. 5 is a functional block diagram including an example implementationof the battery switching control module 480. As shown, the batteryswitching control module 480 includes a switch selection module 502, acounter 504, and a monitoring module 506.

The switch selection module 502 determines the switch control signals toapply to the switches 374, 376, and 378 based on the voltage and/orcurrent commands. For instance, the switch selection module 502 candetermine the switch control using one or more equations and/or lookuptables that relate the voltage and/or current commands to batteryvoltage levels and output the switch control signals 481 to the battery199.

As described in greater detail below, the counter 504 can increment atime counter based on the switch configuration indicated by the switchcontrol signals 481 and provide a counter signal 482 to the monitoringmodule 506 indicative of the time counter. The counter 504 can alsocompare the time counter with a dwell time in which each of the switches374, 376, and 378 are open. In an implementation, the dwell timecorresponds to the time when the battery 199 transitions from the firstvoltage operating state to the second voltage operating state, or viceversa, and the switches 374, 376, and 378 are open to mitigate damageand/or drive torque disturbance.

The monitoring module 506 monitors the voltage and/or current commands460 and the DC bus voltage and/or capacitor voltage 410 as measured bythe voltage sensor 411. The monitoring module 506 provides signalsindicative of the voltage, the current commands, the DC bus voltage,and/or capacitor voltage to the switch selection module 502. FIG. 6 is agraph 600 illustrating the approximate capacitor voltages at thecapacitor 380.

The value of the capacitor 380 can be selected such that the storedcharge is used by the motor 198 when the battery transitions from thesecond voltage operating state to the first voltage operating state. Thevalue of the capacitor 380 can be derived using the following equation:

Tdw=½C([Vst2]²−[Vst1]²)/(rpm*Nm*2 pi/60)+Δ(t)  Eq. 1, which can berewritten as:

C=2*(Tdw−Δ(t))*(rpm*Nm*2 pi/60)/([Vst2]²−[Vst1]²)

where Tdw is the dwell time, C is the capacitance value of capacitor380, Vst2 is the voltage corresponding to the second voltage operatingstate, Vst1 is the voltage corresponding to the first voltage operatingstate, rpm represents the revolutions per minute of the motor 198, Nmrepresents the torque of the motor 198, and Δ(t) is a predeterminedslack time parameter.

FIG. 7 is a flowchart depicting an example method 700 for switching thebattery 199 from the second voltage operating state to the first voltageoperating state in which switch 376 is initially closed and switches 374and 378 are initially open. The method 700 begins with 704 where theswitch selection module 502 receives one or more voltage and/or currentcommands to transition the battery 199 from the second voltage operatingstate to the first voltage operating state. Based on the voltage and/orcurrent commands, the switch selection module 502 opens the switch 376at 708. At 712, the monitoring module 506 monitors the voltage of thecapacitor 380.

At 716, the monitoring module 506 determines whether the absolute valueof the difference between the capacitor voltage and a predeterminedvoltage value corresponding to the first voltage operating state (Vst1)is less than a predetermined voltage parameter. If the absolute value ofthe difference is not less than the predetermined voltage parameter, themethod 700 returns to 716. If the absolute value of the difference isless than or equal to the predetermined voltage parameter, themonitoring module 506 provides a signal to the switch selection module502 to close switches 374 and 378 at 720.

FIG. 8 is a flowchart depicting an example method 800 for switching thebattery 199 from the first voltage operating state to the second voltageoperating state in which switch 376 is initially open and switches 374and 378 are initially closed. The method 800 begins with 804 where theswitch selection module 502 receives one or more voltage and/or currentcommands to transition the battery 199 from the first voltage operatingstate to the second voltage operating state. Based on the voltage and/orcurrent commands, the switch selection module 502 opens the switch 374and 376 at 808. At 812, the monitoring module 506 monitors the batterycurrent and the counter module 504 increments the time counter. Themotor operates as a generator that charges the capacitor to a highervoltage level.

At 816, the monitoring module 506 determines whether the time counter isgreater than the dwell time. If the time counter is not greater than thedwell time, the method 800 returns to 816. At 820, the monitoring module506 determines whether the battery current equals zero. If the batterycurrent does not equal zero, the method 800 terminates operation at 824.If the battery current equals zero, the monitoring module 506 provides asignal to the switch selection module 502 so that the switch selectionmodule 502 can generate switch control signals to close switch 376 at828.

The foregoing description is merely illustrative in nature and is in noway intended to limit the disclosure, its application, or uses. Thebroad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent upon a study of the drawings, thespecification, and the following claims. It should be understood thatone or more steps within a method may be executed in different order (orconcurrently) without altering the principles of the present disclosure.Further, although each of the embodiments is described above as havingcertain features, any one or more of those features described withrespect to any embodiment of the disclosure can be implemented in and/orcombined with features of any of the other embodiments, even if thatcombination is not explicitly described. In other words, the describedembodiments are not mutually exclusive, and permutations of one or moreembodiments with one another remain within the scope of this disclosure.

Spatial and functional relationships between elements (for example,between modules, circuit elements, semiconductor layers, etc.) aredescribed using various terms, including “connected,” “engaged,”“coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and“disposed.” Unless explicitly described as being “direct,” when arelationship between first and second elements is described in the abovedisclosure, that relationship can be a direct relationship where noother intervening elements are present between the first and secondelements, but can also be an indirect relationship where one or moreintervening elements are present (either spatially or functionally)between the first and second elements. As used herein, the phrase atleast one of A, B, and C should be construed to mean a logical (A OR BOR C), using a non-exclusive logical OR, and should not be construed tomean “at least one of A, at least one of B, and at least one of C.”

In the figures, the direction of an arrow, as indicated by thearrowhead, generally demonstrates the flow of information (such as dataor instructions) that is of interest to the illustration. For example,when element A and element B exchange a variety of information butinformation transmitted from element A to element B is relevant to theillustration, the arrow may point from element A to element B. Thisunidirectional arrow does not imply that no other information istransmitted from element B to element A. Further, for information sentfrom element A to element B, element B may send requests for, or receiptacknowledgements of, the information to element A.

In this application, including the definitions below, the term “module”or the term “controller” may be replaced with the term “circuit.” Theterm “module” may refer to, be part of, or include: an ApplicationSpecific Integrated Circuit (ASIC); a digital, analog, or mixedanalog/digital discrete circuit; a digital, analog, or mixedanalog/digital integrated circuit; a combinational logic circuit; afield programmable gate array (FPGA); a processor circuit (shared,dedicated, or group) that executes code; a memory circuit (shared,dedicated, or group) that stores code executed by the processor circuit;other suitable hardware components that provide the describedfunctionality; or a combination of some or all of the above, such as ina system-on-chip.

The module may include one or more interface circuits. In some examples,the interface circuits may include wired or wireless interfaces that areconnected to a local area network (LAN), the Internet, a wide areanetwork (WAN), or combinations thereof. The functionality of any givenmodule of the present disclosure may be distributed among multiplemodules that are connected via interface circuits. For example, multiplemodules may allow load balancing. In a further example, a server (alsoknown as remote, or cloud) module may accomplish some functionality onbehalf of a client module.

The term code, as used above, may include software, firmware, and/ormicrocode, and may refer to programs, routines, functions, classes, datastructures, and/or objects. The term shared processor circuitencompasses a single processor circuit that executes some or all codefrom multiple modules. The term group processor circuit encompasses aprocessor circuit that, in combination with additional processorcircuits, executes some or all code from one or more modules. Referencesto multiple processor circuits encompass multiple processor circuits ondiscrete dies, multiple processor circuits on a single die, multiplecores of a single processor circuit, multiple threads of a singleprocessor circuit, or a combination of the above. The term shared memorycircuit encompasses a single memory circuit that stores some or all codefrom multiple modules. The term group memory circuit encompasses amemory circuit that, in combination with additional memories, storessome or all code from one or more modules.

The term memory circuit is a subset of the term computer-readablemedium. The term computer-readable medium, as used herein, does notencompass transitory electrical or electromagnetic signals propagatingthrough a medium (such as on a carrier wave); the term computer-readablemedium may therefore be considered tangible and non-transitory.Non-limiting examples of a non-transitory, tangible computer-readablemedium are nonvolatile memory circuits (such as a flash memory circuit,an erasable programmable read-only memory circuit, or a mask read-onlymemory circuit), volatile memory circuits (such as a static randomaccess memory circuit or a dynamic random access memory circuit),magnetic storage media (such as an analog or digital magnetic tape or ahard disk drive), and optical storage media (such as a CD, a DVD, or aBlu-ray Disc).

The apparatuses and methods described in this application may bepartially or fully implemented by a special purpose computer created byconfiguring a general purpose computer to execute one or more particularfunctions embodied in computer programs. The functional blocks,flowchart components, and other elements described above serve assoftware specifications, which can be translated into the computerprograms by the routine work of a skilled technician or programmer.

The computer programs include processor-executable instructions that arestored on at least one non-transitory, tangible computer-readablemedium. The computer programs may also include or rely on stored data.The computer programs may encompass a basic input/output system (BIOS)that interacts with hardware of the special purpose computer, devicedrivers that interact with particular devices of the special purposecomputer, one or more operating systems, user applications, backgroundservices, background applications, etc.

The computer programs may include: (i) descriptive text to be parsed,such as HTML (hypertext markup language), XML (extensible markuplanguage), or JSON (JavaScript Object Notation) (ii) assembly code,(iii) object code generated from source code by a compiler, (iv) sourcecode for execution by an interpreter, (v) source code for compilationand execution by a just-in-time compiler, etc. As examples only, sourcecode may be written using syntax from languages including C, C++, C#,Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl,Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5threvision), Ada, ASP (Active Server Pages), PHP (PHP: HypertextPreprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, VisualBasic®, Lua, MATLAB, SIMULINK, and Python®.

What is claimed is:
 1. An electric motor control system, comprising: acurrent command module configured to, based on a motor torque request, amotor speed, a direct current (DC) bus voltage for an electric motor ofthe vehicle, generate a d-axis current command for the electric motorand a q-axis current command for the electric motor; a voltage commandmodule configured to generate voltage commands based on the d-axiscurrent command and the q-axis current command; and a battery switchingcontrol module configured to: determine a voltage operating state of abattery based on the voltage commands; compare a battery parameter to atleast one of a predetermined voltage parameter and a predeterminedcurrent parameter during a dwell time when a plurality of switches ofthe battery are open; and generate a switch control signal to transitionat least one switch of the plurality of switches to cause the battery tooperate in the voltage operating state based on the comparison.
 2. Theelectric motor control system as recited in claim 1, wherein the dwelltime corresponds to a time period between a first voltage operatingstate and a second voltage operating state.
 3. The electric motorcontrol system as recited in claim 1, wherein the battery parametercomprises at least one of a measured voltage and a measured current. 4.The electric motor control system as recited in claim 1, furthercomprising an inverter module connected between the battery and theelectric motor.
 5. The electric motor control system as recited in claim4, wherein the inverter module is configured to convert voltage providedby the battery and provide the converted voltage to the motor.
 6. Theelectric motor control system as recited in claim 4, further comprisinga capacitor disposed between the battery and the inverter module,wherein the capacitor stores energy provided by the battery.
 7. Theelectric motor control system as recited in claim 6, wherein acapacitance value of the capacitor is selected according toC=2*(Tdw−Δ(t))*(rpm*Nm*2 pi/60)/([Vst2]²−[Vst1]²), where Tdw correspondsto the dwell time, Vst2 is a voltage corresponding to a second voltageoperating state, Vst1 is a voltage corresponding to a first voltageoperating state, rpm corresponds to revolutions per minute of the motor,Nm corresponds to a torque of the motor, and Δ(t) is a predeterminedslack time parameter.
 8. The electric motor control system as recited inclaim 1, wherein the battery comprises at least a first battery and asecond battery.
 9. The electric motor control system of claim 8 whereinthe first battery includes a rating of greater than 60 volts directcurrent (DC), and the second battery includes a rating of greater than60 volts DC.
 10. The electric motor control system as recited in claim8, wherein the plurality of switches are arranged so that the firstbattery and the second battery operate in parallel in a first voltageoperating state and operate in series in a second voltage operatingstate.
 11. An electric motor control method, comprising: based on amotor torque request, a motor speed, a direct current (DC) bus voltagefor an electric motor of the vehicle, generating a d-axis currentcommand for the electric motor and a q-axis current command for theelectric motor; generating voltage commands based on the d-axis currentcommand and the q-axis current command; determining a voltage operatingstate of a battery based on the voltage commands; comparing a batteryparameter to at least one of a predetermined voltage parameter and apredetermined current parameter during a dwell time when a plurality ofswitches of the battery are open; and generating a switch control signalto transition at least one switch of the plurality of switches to causethe battery to operate in the voltage operating state based on thecomparison.
 12. The electric motor control method as recited in claim11, wherein the dwell time corresponds to a time period between a firstvoltage operating state and a second voltage operating state.
 13. Theelectric motor control method as recited in claim 11, wherein thebattery parameter comprises at least one of a measured voltage and ameasured current.
 14. The electric motor control method as recited inclaim 11, further comprising selectively switching an inverter moduleconnected between the battery and the electric motor.
 15. The electricmotor control method as recited in claim 14 further comprising, by theinverter module, converting voltage provided by the battery andproviding the converted voltage to the motor.
 16. The electric motorcontrol method as recited in claim 14 further comprising, by a capacitorconnected between the battery and the inverter module, storing energyprovided by the battery.
 17. The electric motor control method asrecited in claim 16 further comprising selecting a capacitance of thecapacitor according toC=2*(Tdw−Δ(t))*(rpm*Nm*2 pi/60)/([Vst2]²−[Vst1]²), where Tdw correspondsto the dwell time, Vst2 is a voltage corresponding to a second voltageoperating state, Vst1 is a voltage corresponding to a first voltageoperating state, rpm corresponds to revolutions per minute of the motor,Nm corresponds to a torque of the motor, and Δ(t) is a predeterminedslack time parameter.
 18. The electric motor control method as recitedin claim 11, wherein the battery comprises at least a first battery anda second battery.
 19. The electric motor control method of claim 18wherein the first battery includes a rating of greater than 60 voltsdirect current (DC), and the second battery includes a rating of greaterthan 60 volts DC.
 20. The electric motor control method as recited inclaim 18 further comprising: switching the plurality of switches suchthat the first battery and the second battery are connected in parallelin a first voltage operating state; and switching the plurality ofswitches such that the first battery and the second battery areconnected in series in a second voltage operating state.